Semiconductor microfabrication employs a lithography process using a resist composition. In lithography, theoretically, the shorter the exposure wavelength becomes, the higher the resolution can be made, as expressed by Rayleigh's diffraction limit formula. The wavelength of an exposure light source for lithography used in the manufacture of semiconductor devices has been shortened year by year as g line having a wavelength of 436 nm, i line having a wavelength of 365 nm, KrF excimer laser having a wavelength of 248 nm and ArF excimer laser having a wavelength of 193 nm. Further, as the exposure light source of the subsequent generation, soft X ray (EUV) having a wavelength of 13 nm or shorter has been proposed as the exposure light source.
As line width has become narrower in lithography process using light sources having shorter wavelength, such as excimer laser and the like, especially line edge roughness (roughness of pattern surfaces or wave of pattern, abbreviated by LER), as well as resolution, sensitivity and pattern shape, has become important subject (e.g. Proc. of SPIE Vol. 5038 (2003), 689-698).
With further advance of microfabrication technology, it is required for new photoresist compositions to show more advantageous abilities than conventional photoresists. Specifically, photoresist compositions giving better resolution, sensitivity, pattern profiles to resist pattern obtained therefrom, especially giving better line edge roughness are required.